A soy protein adhesive synergistically enhanced by double nanoparticles and preparation method thereof

Abstract

The present invention relates to the technical field of biomass adhesives, and specifically to a soy protein adhesive with synergistic enhancement of double nanoparticles and a preparation method thereof. The raw materials of the soy protein adhesive include the following components in parts by weight: 25-30 parts of soybean meal, 0.8-3.2 parts of nanoparticles and 0.2-2 parts of thiolated halloysite nanotubes; the raw materials of the nanoparticles include: cinnamaldehyde, tannic acid and iron ions; the preparation method of the nanoparticles includes: preparing a solution containing the raw materials of the nanoparticles by ultrasonic treatment. The soy protein adhesive of the present invention has strong mechanical strength, water resistance, toughness and mildew resistance, and at the same time, the raw material source is wide, the cost is low, and it does not rely on fossil energy, the preparation process is simple, and it is easy to be applied in large-scale industrial production, and has a high value of promotion and application.

Description

Technical Field

[0001] The invention relates to the technical field of biomass adhesives, and in particular to a soybean protein adhesive synergistically enhanced by double nanoparticles and a preparation method thereof. Background Art

[0002] Most adhesives used in the wood industry are trialdehyde resins, and the release of formaldehyde or phenol during their use is harmful to the environment and human health. At the same time, such adhesives are overly dependent on petrochemical energy. Using natural materials to prepare green adhesives to replace the above adhesives is of great significance for the large-scale industrial application of adhesives. At present, soy protein, starch and lignin are ideal sources of natural materials, which can be used to develop truly formaldehyde-free biomass adhesives. Among them, soy protein exhibits many ideal properties, such as wide sources, low cost, biodegradability, richness, and rich active groups (amino, carboxyl, hydroxyl, thiol), which have a variety of surface chemical options when combined with compounds. However, weak mechanical properties and poor water resistance limit the widespread use of soy protein adhesives.

[0003] In order to meet the requirements of industrial applications, most of the current research focuses on various modification methods of adhesives. These include physical modification, cross-linking modification, bionic modification and composite modification. Although existing studies have shown that epoxy cross-linkers can significantly improve the mechanical strength of adhesives, cross-linking modification will increase the brittleness of adhesives. Moreover, most of the raw materials for synthesizing cross-linkers are non-renewable fossil energy, which further limits the widespread use of cross-linkers. For bionic modification, mussel and barnacle bionics are currently used to prepare adhesives with high adhesion suitable for underwater use. However, the use of polydopamine in its technical solution greatly increases the cost of adhesives, so bionic modification has not been widely used in industrial production. In addition, soy protein-based adhesives are usually rich in nutrients such as protein and polysaccharides, which makes the adhesives easily eroded by microorganisms under high humidity conditions, causing cementation damage. In order to improve the mildew resistance of soy protein adhesives, preservatives are usually added to the adhesives. However, this also mainly relies on non-renewable fossil energy, which runs counter to the goal of green and sustainable development. In recent years, natural antibacterial materials, such as chitosan and antimicrobial peptides, have attracted widespread attention from researchers due to their good antibacterial properties and renewable advantages. The introduction of chitosan has been proven to enhance the mildew resistance of adhesives. However, unmodified chitosan is difficult to strongly cross-link with the protein matrix, and has limited effect on improving the mechanical properties of adhesives. The cost factor of antimicrobial peptides makes it difficult to apply them to the field of wood adhesives on a large scale.

[0004] Therefore, how to use natural materials to design a soybean protein adhesive with high shear strength, high toughness, good water resistance, good mildew resistance and low cost remains a technical problem that needs to be solved urgently in this field. Summary of the invention

[0005] In view of this, the present invention first provides a soybean protein adhesive, the raw materials of which include the following components by weight: 25-30 parts of soybean meal, 0.8-3.2 parts of nanoparticles and 0.2-2 parts of thiolated halloysite nanotubes;

[0006] The raw materials of the nanoparticles include: cinnamaldehyde, tannic acid and iron ions;

[0007] The method for preparing the nanoparticles comprises: subjecting a solution containing nanoparticle raw materials to ultrasonic treatment to obtain the nanoparticles.

[0008] The inventive concept of the present invention is as follows: a soybean protein adhesive with excellent performance is prepared by rationally selecting synthetic raw materials, designing cross-linking methods and chemical structures, and combining energy dissipation mechanisms.

[0009] The present invention constructs a polymer matrix-nanoparticle structure through five interactions such as Schiff base, disulfide bond, ion chelation, electrostatic interaction and intermolecular hydrogen bonding, and utilizes cinnamaldehyde-tannic acid-iron ion nanoparticles and thiolated halloysite nanotube double nanoparticles to significantly improve the shear strength, toughness, water resistance and mildew resistance of the soy protein adhesive.

[0010] In the adhesive system of the present invention, cinnamaldehyde-tannic acid-iron ion nanospheres and thiolated halloysite nanotubes are tightly connected to soybean protein through multiple covalent bonds and non-covalent bonds, thereby improving the crosslinking density in the adhesive system, and nanoparticles of different shapes and sizes are uniformly filled in the polymer system. This unique polymer-nanoparticle structure greatly improves the mechanical strength, water resistance, toughness and mildew resistance of the soybean protein adhesive. Among them, cinnamaldehyde is a natural organic active ingredient that exerts antibacterial effects through various mechanisms such as antifungal, antiparasitic, insecticidal and anti-inflammatory. The active aldehyde group contributes to chemical crosslinking and can produce tight crosslinking with soybean protein through covalent bonds. However, its strong hydrophobicity limits its application. Emulsification is an effective method to improve the water solubility of hydrophobic substances. Tannic acid is a water-soluble polyphenol compound that is widely present in higher plants. It plays an important role in protecting plants from fungal or bacterial erosion due to its ability to form complexes with proteins, polysaccharides and metals. At the same time, tannic acid has a strong chelating ability and can form a tannic acid-metal ion complex with metal ions through strong ionic crosslinking, and this structure is beneficial to energy dissipation. The present invention uses the self-assembly characteristics between oily cinnamaldehyde and aqueous tannic acid-metal complexes to uniformly disperse hydrophobic cinnamaldehyde molecules in a hydrophilic tannic acid solution in the absence of a surfactant to prepare cinnamaldehyde-tannic acid-iron ion nanoparticles. In addition, the cinnamaldehyde, tannic acid and trivalent iron ions of the present invention all have antibacterial properties, so that the addition of cinnamaldehyde-tannic acid-iron ion nanoparticles greatly enhances the mildew resistance of the soy protein adhesive.

[0011] As a preferred embodiment of the present invention, the preparation method of the cinnamaldehyde-tannic acid-iron ion nanoparticles comprises:

[0012] (1) dissolving cinnamaldehyde in ethanol and dissolving tannic acid in water; mixing the cinnamaldehyde ethanol solution and the tannic acid aqueous solution and then subjecting them to ultrasonic treatment to obtain a cinnamaldehyde-tannic acid nanoparticle emulsion;

[0013] (2) Dissolve ferric chloride in water, then add the ferric chloride aqueous solution dropwise into the cinnamaldehyde-tannic acid nanoparticle emulsion, and prepare cinnamaldehyde-tannic acid-iron ion nanoparticles after ultrasonic treatment.

[0014] In a specific implementation process, the emulsion after ultrasonic treatment in step (2) can be placed at -50°C±20°C for more than 12 hours, and then freeze-dried to obtain dry cinnamaldehyde-tannic acid-iron ion nanoparticles.

[0015] As a preferred embodiment of the present invention, the weight ratio of soybean meal, the nanoparticles and thiolated halloysite nanotubes is 1:0.02-0.12:0.007-0.08.

[0016] As a preferred embodiment of the present invention, the weight ratio of the nanoparticles to the thiolated halloysite nanotubes is 1 to 3:1.

[0017] As a preferred embodiment of the present invention, the raw material of the soybean protein adhesive further includes a chemical cross-linking agent, and the chemical cross-linking agent is at least one of triglycidylamine, glycerol triglycidyl ether or ethylene glycol triglycidyl ether.

[0018] As a preferred embodiment of the present invention, the weight ratio of the chemical cross-linking agent to the soybean meal is 5 to 8:100.

[0019] As a preferred embodiment of the present invention, the raw material of the soybean protein adhesive also includes water; the weight ratio of water to soybean meal is 2 to 3:1.

[0020] As a preferred embodiment of the present invention, the raw materials of the soy protein adhesive include the following components in parts by weight:

[0021] 25-30 parts of soybean meal, 1.4-2 parts of chemical cross-linking agent, 0.8-3.2 parts of the nanoparticles, 0.2-2 parts of thiolated halloysite nanotubes and 69.9-72 parts of water.

[0022] As a preferred embodiment of the present invention, the raw materials of the soy protein adhesive include the following components in parts by weight:

[0023] 27-29 parts of soybean meal, 1.3-1.7 parts of chemical cross-linking agent, 0.8-3.2 parts of the nanoparticles, 0.2-2 parts of thiolated halloysite nanotubes and 69.9-72 parts of water.

[0024] Furthermore, the present invention also provides a method for preparing the soybean protein adhesive in any of the above embodiments, comprising the following steps:

[0025] (1) dispersing soybean meal, nanoparticles and a chemical crosslinking agent in water to prepare a first dispersion; dispersing thiolated halloysite nanotubes in water to prepare a second dispersion;

[0026] (2) The first dispersion liquid and the second dispersion liquid are mixed and stirred at 80-90° C. to obtain the soybean protein adhesive.

[0027] As a preferred embodiment of the present invention, the thiolated halloysite nanotubes are obtained by modifying the halloysite nanotubes with a silane coupling agent.

[0028] Thiol groups and disulfide bonds are very important groups in proteins. The formation of disulfide bonds is crucial to the protein structure, and the number of disulfide bonds affects the gel properties, crosslinking density and rheological properties of proteins. The thiol-modified halloysite nanotubes obtained by modifying the halloysite nanotubes with silane coupling agents can further improve the shear strength, toughness and water resistance of the soy protein adhesive of the present invention.

[0029] As a preferred embodiment of the present invention, the preparation method of the thiolated halloysite nanotubes comprises: mixing a toluene solution of 5% to 15% by volume of 3-mercaptopropyltrimethoxysilane with halloysite nanotubes, and then ultrasonically treating at 0°C ± 4°C and separating the solid to obtain the thiolated halloysite nanotubes.

[0030] Preferably, the thiolated halloysite nanotubes are prepared by ultrasonic treatment for more than 30 minutes in an ice bath environment and then separating the solid by centrifugation.

[0031] In a specific implementation process, in order to remove the free silane coupling agent as much as possible, the solid is washed with methanol, including but not limited to.

[0032] In a specific implementation process, the separated solid can be dried to obtain thiolated halloysite nanotubes.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The soybean protein adhesive of the present invention has strong mechanical strength, water resistance, toughness and mildew resistance, and has a wide range of raw material sources, low cost, and is independent of fossil energy. The preparation process is simple and can be easily applied in large-scale industrial production, thus having a high value for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the shear strength of soy protein adhesive.

[0036] Figure 2 This is a schematic diagram of the toughness of the cured adhesive layer of soy protein adhesive.

[0037] Figure 3 This is a schematic diagram of the anti-mildew performance of soybean protein adhesive.

[0038] Figure 4 This is a scanning electron microscope image of the cross section of the cured adhesive layer of the soy protein adhesive. DETAILED DESCRIPTION

[0039] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0040] In the examples and comparative examples, if no specific techniques or conditions are specified, all are carried out according to conventional methods or techniques or conditions described in the literature in the field, or according to the product instructions. The reagents and instruments used, if no manufacturer is specified, are all conventional products that can be purchased through regular channels.

[0041] The preparation method of the cinnamaldehyde-tannic acid-iron ion nanoparticles used in the following examples and comparative examples is:

[0042] a. Under magnetic stirring, 2 g of cinnamaldehyde was uniformly dissolved in 10 ml of ethanol, and 0.5 g of tannic acid was uniformly dissolved in 90 ml of deionized water. The two solutions were mixed and stirred evenly, and ultrasonic treatment was performed for 30 minutes to obtain cinnamaldehyde-tannic acid nanoemulsion;

[0043] b. Under magnetic stirring, 0.25 g of ferric chloride was uniformly dissolved in 10 ml of deionized water, and the ferric chloride solution was added dropwise to the above cinnamaldehyde - tannic acid nanoemulsion, stirred and then treated with ultrasound for 30 minutes to obtain cinnamaldehyde - tannic acid - iron ion nanoemulsion;

[0044] c. The cinnamaldehyde-tannic acid-iron ion nanoemulsion was stored in an ultra-low temperature refrigerator at -50°C for 12 hours, and dry cinnamaldehyde-tannic acid-iron ion nanoparticles were obtained by freeze drying.

[0045] The preparation method of the thiolated halloysite nanotubes used in the following examples and comparative examples is:

[0046] a. 1 g of halloysite nanotubes was uniformly dispersed in 10 ml of anhydrous toluene by mechanical stirring, and then 1 ml of 3-mercaptopropyltrimethoxysilane was slowly added dropwise;

[0047] b. The suspension was sonicated for 30 minutes under an ice bath and then centrifuged (8000 rpm, 5 minutes) to obtain a solid phase of the mixture;

[0048] c. The solid phase was washed three times with methanol to remove the free silane coupling agent, and then vacuum dried at 80° C. for 12 hours to obtain thiolated halloysite nanotubes.

[0049] The preparation method of the cinnamaldehyde-tannic acid nanoparticles used in the following comparative example is:

[0050] Under magnetic stirring, 2 g of cinnamaldehyde was uniformly dissolved in 10 ml of ethanol, and 0.5 g of tannic acid was uniformly dissolved in 90 ml of deionized water. The two solutions were mixed and stirred uniformly, and ultrasonic treatment was performed for 30 minutes to obtain cinnamaldehyde-tannic acid nanoemulsion, and then cinnamaldehyde-tannic acid nanoparticles were obtained by freeze drying.

[0051] The preparation method of the tannic acid-iron ion nanoparticles used in the following comparative example is:

[0052] a. Under magnetic stirring, 0.5 g of tannic acid was uniformly dissolved in 90 ml of deionized water and ultrasonically treated for 30 minutes to obtain a tannic acid solution;

[0053] b. Under magnetic stirring, 0.25 g of ferric chloride was uniformly dissolved in 10 ml of deionized water, the ferric chloride solution was added dropwise to the tannic acid solution, stirred and then treated with ultrasound for 30 minutes to obtain a tannic acid - iron ion solution;

[0054] c. The tannic acid-iron ion solution was stored in an ultra-low temperature refrigerator at -50°C for 12 hours, and dry tannic acid-iron ion nanoparticles were obtained by freeze drying.

[0055] "Parts" in the following examples all represent parts by weight.

[0056] The crosslinking agent used in the following examples and comparative examples is triglycidylamine.

[0057] Example 1

[0058] This embodiment provides a soybean protein adhesive, and the specific preparation method is as follows:

[0059] a. A mixture of 28 parts by weight of soybean meal, 1.6 parts by weight of cinnamaldehyde - tannic acid - iron ion nanoparticles and 1.5 parts by weight of a cross-linking agent was uniformly dispersed in 50 parts of deionized water and stirred for 10 minutes;

[0060] b. 0.8 parts by weight of thiolated halloysite nanotubes were uniformly dispersed in 19.6 parts by weight of deionized water and mechanically stirred for 10 minutes;

[0061] c. The dispersions obtained in steps a and b were mixed and mechanically stirred in a water bath at 85°C for 20 minutes to obtain a soy protein adhesive.

[0062] Example 2

[0063] This embodiment provides a soybean protein adhesive, and the specific preparation method is as follows:

[0064] a. A mixture of 28 parts by weight of soybean meal, 0.8 parts by weight of cinnamaldehyde - tannic acid - iron ion nanoparticles and 1.5 parts by weight of a cross-linking agent was uniformly dispersed in 50 parts of deionized water and stirred for 10 minutes;

[0065] b. 0.4 parts by weight of thiolated halloysite nanotubes were uniformly dispersed in 20.8 parts by weight of deionized water and mechanically stirred for 10 minutes;

[0066] c. The dispersions obtained in steps a and b were mixed and mechanically stirred in a water bath at 85°C for 20 minutes to obtain a soy protein adhesive.

[0067] Example 3

[0068] This embodiment provides a soybean protein adhesive, and the specific preparation method is as follows:

[0069] a. A mixture of 28 parts by weight of soybean meal, 3.2 parts by weight of cinnamaldehyde - tannic acid - iron ion nanoparticles and 1.5 parts by weight of a cross-linking agent was uniformly dispersed in 50 parts of deionized water and stirred for 10 minutes;

[0070] b. 1.4 parts by weight of thiolated halloysite nanotubes were uniformly dispersed in 17.4 parts by weight of deionized water and mechanically stirred for 10 minutes;

[0071] c. The dispersions obtained in steps a and b were mixed and mechanically stirred in a water bath at 85°C for 20 minutes to obtain a soy protein adhesive.

[0072] Comparative Example 1

[0073] This comparative example provides a soybean protein adhesive, and the specific preparation method is as follows:

[0074] A mixture of 28 parts by weight of soybean meal and 1.5 parts of a cross-linking agent was dispersed in 82 parts of water, and stirred for 20 minutes under heating in a water bath at 85° C. to obtain a uniform soybean protein adhesive.

[0075] Comparative Example 2

[0076] This comparative example provides a soybean protein adhesive, and the specific preparation method is as follows:

[0077] A mixture of 28 parts by weight of soybean meal, 1.2 parts by weight of cinnamaldehyde-tannic acid nanoparticles and 1.5 parts by weight of a cross-linking agent was uniformly dispersed in 70.8 parts of deionized water, and stirred for 20 minutes under heating at 85° C. in a water bath to obtain a uniform soybean protein adhesive.

[0078] Comparative Example 3

[0079] This comparative example provides a soybean protein adhesive, and the specific preparation method is as follows:

[0080] A mixture of 28 parts by weight of soybean meal, 1.2 parts by weight of tannic acid-iron ion nanoparticles and 1.5 parts by weight of a cross-linking agent was uniformly dispersed in 70.8 parts of deionized water, and stirred for 20 minutes under heating at 85° C. in a water bath to obtain a uniform soybean protein adhesive.

[0081] Comparative Example 4

[0082] This comparative example provides a soybean protein adhesive, and the specific preparation method is as follows:

[0083] A mixture of 28 parts by weight of soybean meal, 1.6 parts by weight of cinnamaldehyde-tannic acid-iron ion nanoparticles and 1.5 parts by weight of a cross-linking agent was uniformly dispersed in 70.4 parts of deionized water, and stirred for 20 minutes under heating at 85° C. in a water bath to obtain a uniform soybean protein adhesive.

[0084] Comparative Example 5

[0085] This comparative example provides a soybean protein adhesive, and the specific preparation method is as follows:

[0086] A mixture of 28 parts by weight of soybean meal, 0.8 parts by weight of thiolated halloysite nanotubes and 1.5 parts by weight of a crosslinking agent was uniformly dispersed in 70.6 parts of deionized water, and stirred for 20 minutes under heating in a water bath at 85° C. to obtain a uniform soybean protein adhesive.

[0087] Test example

[0088] The soybean protein adhesives prepared in the examples and comparative examples were tested according to the national standard GB / T17657-2013. Figure 1 As shown in the results, the synergistic addition of cinnamaldehyde-tannic acid-iron ion nanoparticles and thiolated halloysite nanotubes significantly enhanced the dry / wet shear strength of the soy protein adhesive.

[0089] The toughness of the soybean protein adhesive was analyzed by observing the cured adhesive layer of the soybean protein adhesive prepared in the examples and comparative examples. Figure 2 As shown, the results showed that the synergistic addition of cinnamaldehyde-tannic acid-iron ion nanoparticles and thiolated halloysite nanotubes significantly enhanced the toughness of the soy protein adhesive.

[0090] The mildew resistance of the soybean protein adhesive was analyzed by observing the surface mildew behavior of the soybean protein adhesive prepared in the examples and comparative examples at room temperature. Figure 3 As shown in the figure, the addition of cinnamaldehyde-tannic acid-iron ion nanoparticles significantly prolonged the shelf life of the soy protein adhesive. The improvement of the anti-mildew performance of the adhesive obtained by adding only tannic acid-iron ion nanoparticles was limited.

[0091] The cross-linking density of the adhesive system was analyzed by taking scanning electron microscope images of the cross-section of the cured adhesive layer of the soy protein adhesive. Figure 4 As shown in the figure, the addition of cinnamaldehyde-tannic acid-iron ion nanoparticles makes the adhesive microstructure denser.

[0092] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A soybean protein adhesive, It is characterized in that The raw materials include the following components by weight: 25-30 parts of soybean meal, 0.8-3.2 parts of nanoparticles and 0.2-2 parts of thiolated halloysite nanotubes; The raw materials of the nanoparticles include: cinnamaldehyde, tannic acid and iron ions; The method for preparing the nanoparticles comprises: subjecting a solution containing nanoparticle raw materials to ultrasonic treatment; The raw materials of the soybean protein adhesive also include a chemical crosslinking agent, and the chemical crosslinking agent is triglycidylamine; the weight ratio of the chemical crosslinking agent to soybean meal is (5-8):

100.

2. The soybean protein adhesive according to claim 1, It is characterized in that The weight ratio of soybean meal, the nanoparticles and thiolated halloysite nanotubes is 1:(0.02-0.12):(0.007-0.08).

3. The soybean protein adhesive according to claim 1, It is characterized in that The weight ratio of the nanoparticles to the thiolated halloysite nanotubes is (1-3):

1.

4. The soybean protein adhesive according to claim 1, It is characterized in that The raw materials of the soybean protein adhesive also include water; the weight ratio of water to soybean meal is (2-3):

1.

5. The soybean protein adhesive according to any one of claims 1 to 4, It is characterized in that Its raw materials include the following components by weight: 25-30 parts of soybean meal, 1.4-2 parts of the chemical cross-linking agent, 0.8-3.2 parts of the nanoparticles, 0.2-2 parts of thiolated halloysite nanotubes and 69.9-72 parts of water.

6. The soybean protein adhesive according to claim 5, It is characterized in that Its raw materials include the following components by weight: 27-29 parts of soybean meal, 1.3-1.7 parts of the chemical cross-linking agent, 0.8-3.2 parts of the nanoparticles, 0.2-2 parts of thiolated halloysite nanotubes and 69.9-72 parts of water.

7. The method for preparing the soybean protein adhesive according to any one of claims 1 to 6, It is characterized in that The steps include: (1) dispersing soybean meal, the nanoparticles and the chemical crosslinking agent in water to obtain a first dispersion; dispersing thiolated halloysite nanotubes in water to obtain a second dispersion; (2) The first dispersion liquid and the second dispersion liquid are mixed and stirred at 80-90° C. to obtain the soybean protein adhesive.

8. The preparation method according to claim 7, It is characterized in that The preparation method of the thiolated halloysite nanotube comprises: mixing a toluene solution of 5% to 15% by volume of 3-mercaptopropyltrimethoxysilane with the halloysite nanotube, and then subjecting the mixture to ultrasonic treatment at 0°C±4°C and separating the solid to obtain the thiolated halloysite nanotube.

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